FIELD OF THE INVENTION
The present invention relates to a sanding apparatus of the type comprising a circular backing plate adapted to be secured to one end of a rotatably driven shaft, said backing plate having an outer front face having formed therein a plurality of grooves extending from a peripheral portion to a recessed central portion of the front face of the backing plate, and acting as a support for an abrasive-coated paper disc.
In known sanding apparatus of this type, holes communicating with the grooves of the backing plate may be formed in the abrasive-coated paper disc. The holes formed in the abrasive-coated paper disc and the grooves formed in the front face of the rotating backing plate are intended for ventilating and therefore cooling these elements. Moreover, the grooves formed in the front face of the rotating backing plate are usually curved in a direction opposite the direction of rotation of the backing plate from the central portion to the peripheral portion of the backing plate. In fact, this specific curved configuration of the grooves is directed to improve the ventilation by forcing the air towards the outer periphery of the backing plate.
It is known that sanding apparatus utilizing abrasive-coated paper discs mounted on a rotating circular backing plate generate, like all sanders, a considerable amount of fine particles of dust which are particularly noxious for the operator. In sanding apparatus of the above-mentioned type, comprising a rotating backing plate and an abrasive-coated paper disc, both ventilated, this inconvenience is emphasized by the fact that the ventilation air increases the dispersion of fine dust particles much more than in sanders with non-ventilated rotating backing plate and abrasive-coated paper disc.
On the other hand, sanders, notably of the type used in building construction, which comprise a front-acting grinding wheel secured to the end of a hollow shaft and formed with grooves in its active front surface, are already known in the art. In these known sanders, the grooves communicate with a cavity formed centrally of the active front surface of the grinding wheel, said cavity communicating with the hollow shaft connected to suction means capable of drawing up from the center of grinding the wheel the fine dust particles generated by the grinding wheel (see French Pat. No. 2,212,773). Sanders of this last type, utilizing a front-action grinding wheel, not an abrasive-coated paper disc as in the case of the sanding apparatus contemplated herein, are capable of absorbing the dust completely, thus avoiding the noxious dispersion of fine particles by the grinding wheel.